1. Field of the Invention
This invention relates to a BGA type IC package and the like having a plurality of electrodes arranged on a lower surface thereof. More particularly, it relates to an IC package in which a high density arrangement of external terminals is realized with a small-sized simple structure in such a BGA type IC package and the like.
2. Brief Description of the Prior Art
A typical BGA type IC package includes hundreds of terminals. A group of such terminals is divided into a plurality of unit groups of terminals. The unit groups of terminals are pierced for connection through wiring layers composed of several laminations. The unit terminals are changed in position at the lead patterns provided on each layer. A plurality of external terminals are uniformly rearranged on a lower surface of the lowermost layer.
There are also known other types of conventional IC packages. They are a dual-in-package (DIP) and a quad flat package (QFP).
One type having a large number of IC terminals of finely-pitched arrangement is a tape automated bonding structure (TAB). In this type, an IC is loaded on a thin flat flexible wiring sheet and bonded, and the pitches are changed on the wiring sheet.
However, with the progress in IC technology, the degree of integration is remarkably enhanced, and with the increase in the number of the terminals and in the size of the IC, the package styles of the conventional DIP, QFP and TAB are required to be too large in size. Recently, there were proposed a quad flat non-lead (QFN), a ball grid array (BGA), and a chip size package (CSP) which are all intended to avoid increasing the size of the IC packages. Some of them are already put into actual use.
However, it is necessary for an IC package of this type to have an interposer for rearranging the terminals group of the IC. For example, the BGA type IC package requires three to eight wiring layers as the interposer, depending on the density of the terminals. Accordingly, the structure becomes complicated, a high degree of technique is required, and the cost is very high.
The present invention has been accomplished in view of the above.